1. Field of the Invention
This invention relates to a magnetic recording medium comprising a thin ferromagnetic metal film recording layer provided on a substrate, and more particularly to a magnetic recording medium exhibiting excellent durability and good adhesion between the thin ferromagnetic metal film and the substrate.
2. Description of the Prior Art
Coating type magnetic recording media are widely used. These magnetic recording media are made by dispersing magnetic particles in a binder, applying the obtained dispersion on substrates, and drying this dispersion. In the magnetic recording media of this type, it is impossible to eliminate the use of the binder and there is a limit in minimizing the thickness of the recording media in order to conduct high-density recording.
Recently, so-called non-binder type magnetic recording media using no binders have attracted attention because of their ability to meet strong demand for high density recording. The magnetic recording media of this type have magnetic recording layers which consist of thin ferromagnetic metal films formed by a vapor deposition process such as vacuum deposition, or a plating process such as electroplating or electroless plating. Thus various efforts are being made to develop non-binder type magnetic recording media suitable for practical use.
Particularly, the vacuum deposition process is advantageous in that it requires no waste water treatment unlike the plating process, the process for preparing the recording media is simple, and the film deposition speed is higher than any other processes.
When a magnetic tape comprising a thin ferromagnetic film recording layer formed by vacuum deposition is compared with the conventional coating type magnetic tape, the former exhibits an extremely higher reproduction output and the reproduction output frequency characteristics greatly extending towards the short wavelength side. In order to obtain good magnetic characteristics of the magnetic tape prepared by the vacuum deposition process, it has been proposed to conduct deposition while oxygen is introduced into the vacuum vessel. However, this proposed method is not completely satisfactory with respect to the durability of the magnetic tape obtained and the adhesion between the thin ferromagnetic film and the substrate therefor.